The American weapon, known officially as the Active Denial System (pictured, above), heats the target's skin with short microwaves. These only penetrate to about 1/64 of an inch. That's enough to be extremely painful but (generally) harmless. In thousands of tests of the system, nobody has been able to stay in the beam for more than a few seconds.

The latest version developed by the Pentagon's Joint Non-lethal Weapons Directorate is known as System 2. It weighs nine tons, and because some of the components require supercooling, it takes hours to prepare the weapon for action. A portable version would only require a fraction of the power of the 100-kilowatt System 2, however. The smaller device would also have a range of around 100 feet, heating an area perhaps four inches across, enough to stop or drive away an individual.

Existing Active Denial devices use a gyrotron, a type of free-electron maser. The heart of this a vacuum tube in which electrons are gyrated (hence gyrotron) in a very strong magnetic field. That field requires superconducting magnets, which need to be kept at ultra-low temperatures to function.

The U.S. military is trying to get away from Gyrotrons and replace them with solid-state electronics. Earlier this year Danger Room, reported on a contract for classified work with Gallium Nitrideas "solid state source for use in non-lethal weapons." Like an LED which emits light, this would be much more robust and compact device. Feed in electricity, get microwaves out.

At the same time the JNLWD is looking at infra-red lasers to do the same job. These have disadvantages -– they don't go through clothing as millimeter waves do, for one thing –- but it's much easier to build a portable laser system.

However, the Israeli team is taking a different approach. Researchers at the College of Judea & Samaria (CJS), led by Dr. Moshe Einat, say that they have developed "unique know-how" which will allow them to build portable versions of the Active Denial "based on new research to manufacture small-scale portable gyrotrons." They claim the picture to the right is of a prototype. Einat's team did not respond to Danger Room requests for further information.

The development of the 95 GHz portable gyrotron to be used as the basis for a Stun-Gun prototype would cost approximately $250,000 (U.S.), with the program running 12 months in length.

Even if they can meet this ambitious budget and timescale, they are likely to run into another problem: testing. The U.S. system required several years of human tests, before the military would even consider deploying it, and for various reasons they have yet to give it the green light. However, the Israeli Defense Forces may be persuaded to take a more adventurous approach, having already used new non-lethals such as the malodorant "skunk bomb."

But even if it does not go ahead, the project highlights how other countries could now develop their own versions on a shoestring budget. The U.S. has shown that these short microwaves can be harnessed as a useful non-lethal weapon. If a university department can do it in Israel, so can others in Russia, China or anywhere else. The U.S. has been the leader and sole player in this technology for fifteen years, but that lead may be about to disappear – along with any control over how it is used.